GCSE Computing

  • Created by: Riya.b123
  • Created on: 21-02-19 13:36
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  • The CPU
    • Registers
    • Buses
    • Cache
    • Arithmetic Logic Unit
    • Clock
    • Control unit
      • decoder
  • Control Unit
    • Coordinates actions of computer
    • Sends control signals to other parts of CPU & components of computer
    • Decoder works out what program instructions mean
  • Registers
    • Accumulator - stores calculation results
    • Program Counter - holds address of next instruction to be fetched
    • Memory Data Register - Temporary store for anything copied from memory
    • Memory Address Register - holds address of memory location currently being read or written to
  • Cache Memory
    • very fast memory
    • speeds up processing by storing recently or frequently used instructions
    • As it becomes larger it takes longer to find data so becomes slower
    • Too expensive to use for main memory (RAM) in personal computers
  • Multi-Core Processors
    • contains more than one CPU
    • give fast processing speeds
    • Can work on different tasks at the same time
  • Embedded Systems
    • Components on single printed circuit board - processor, memory
    • Built for small range of specific tasks
    • General purpose
    • Washing machine, digital camera, microwave etc.
  • RAM & ROM
    • Random Access Memory - computer stores data & instructions when application is running
      • Data can be read & written
      • Volatile - data lost when power off
      • Often removable
    • Read Only Memory - stores instructions that don't need  to be changed during normal use
      • Data can be read
      • Non volatile - retains data if power off
  • Virtual Memory
    • slow
    • Disc Thrashing
    • Data Swapping
  • Magnetic Storage
    • used in hard disc drives & digital tapes
    • Data encoded on surface
    • Low cost
    • Large capacity
    • Fast
    • Not portable
    • Durable & Reliable
  • Optical
    • CDs, DVDs, Blue-ray
    • use laser to read & write data
    • Low capacity
    • slow
    • Cheap
    • portable
    • reliable but not durable
  • Solid State
    • Made of flash memory
    • SSDs, SD cards, USBs
    • Moderate capacity
    • Very fast
    • more expensive than magnetic & optical
    • portable
    • reliable
  • LAN
    • a network in a small geographical area
    • manged by local manager or team at site
    • home or school
  • WAN
    • connects several LANs over large geographical area
    • Large companies
    • communicate with computers & users in other locations
    • managed by several people or parts of an organisation
  • Factors affecting network performance
    • Bandwidth
    • Hardware & Software limitations
    • A high number of users
    • High network traffic
  • Client Server Network
    • users log in to access programs & data stored on them
    • servers responsible for security
    • all files backed up centrally
  • Peer To Peer Network
    • no server to manage network
    • each client acts as server
    • security is distributed
    • data stored on each client
    • user responsible for backup
  • The Internet
    • WAN
    • web hosting
    • IP addresses
    • Domain Name Service
  • Topologies
    • Star - each computer connected to a central hub or switch
      • if one fails all the others would work
      • easy to add new devices
      • a lot of cables
    • Mesh - each computer connected to all other computers
      • if one fails there is an alternative route
      • expensive
  • Protocols
    • TCP/IP - allows computers to communicate across a WAN
    • FTP - transfer files
    • HTTP & HTTPS
    • SMTP - emails
    • POP - retrieve emails
    • IMAP - emails read & stored on server
  • Packet Switching
    • data split into small sections
    • packets inspected
    • Packets arrived to user
    • may not be in order
  • Threats to networks
    • Phishing - emails claiming to be from banks etc.
      • Blagging - criminal persuading victim to give personal info
      • Shouldering - finding pins by watching
    • weak passwords
    • Malware
      • virus - program hidden inside another - spread
      • worm - replicate & send emails
      • Trojans - delete files
      • Spyware & Adware
    • Brute force attakcs, data interception & theft, DOS, SQL
  • Prevention of vulnerabilities
    • Penetration testing
    • network forensics
    • anti malware software
    • encryption
    • firewalls
  • Operating system
    • manages user interactions through user interface
    • manages peripheral devices
    • user interface
      • Graphical user interface
    • utility software
      • encryption software
      • data compression
      • defragmentation
    • application software

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